Adjusting RFID waveform shape in view of signal from another reader

ABSTRACT

Systems, software, devices, and methods are described for an RFID reader system to communicate with RFID tags. RF energy encountered in conjunction with using a selected channel is detected. The RF energy can be a signal from another RFID reader. The detected signal is used to adjust a waveform shaping parameter. RF waves can be transmitted from the reader to the RFID tags and RF waves can be backscattered from the RFID tags. At least some of the RF waves transmitted to or backscattered from the RFID tags have a waveform with a shape according to the adjusted waveform shaping parameter.

CLAIMS OF PRIORITY

This application is a continuation in part of U.S. application Ser. No.10/824,049 filed on Apr. 13, 2004, entitled “METHOD AND APPARATUS TOCONFIGURE AN RFID SYSTEM TO BE ADAPTABLE TO A PLURALITY OF ENVIRONMENTALCONDITIONS”.

This application is a continuation in part of U.S. application Ser. No.10/985,518 filed on Nov. 10, 2004, entitled “RFID TAGS ADJUSTING TODIFFERENT REGULATORY ENVIRONMENTS, AND RFID READERS TO SO ADJUST THEMAND METHODS”.

This application is a continuation in part of U.S. application Ser. No.11/195,468 filed on Aug. 1, 2005, entitled “PREVENTING COMMUNICATIONCONFLICT WITH OTHER RFID READERS”.

This application is a continuation in part of U.S. application Ser. No.11/388,235 filed on Mar. 26, 2006, entitled “ERROR RECOVERY IN RFIDREADER SYSTEMS”.

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Application Ser. No. 60/678,903 filed May 4, 2005 entitled“RECORDING USAGE DATA ABOUT RFID CHANNELS”.

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Application Ser. No. 60/709,253 filed Aug. 17, 2005 entitled“PREVENTING COMMUNICATION CONFLICT AMONG RFID READERS”.

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Application Ser. No. 60/715,917 filed Sep. 9, 2005 entitled“RFID READER SYSTEM CHANGING MODES IN RESPONSE TO DETECTING POSSIBLE TAGREAD ERRORS”.

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Application Ser. No. 60/751,328 filed Dec. 16, 2005 entitled“RECORDING USAGE DATA ABOUT RFID CHANNELS”.

The entire content of each of the above applications is incorporatedherein by reference.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application may be found to be related to U.S. patentapplication entitled: “ADJUSTING RFID WAVEFORM SHAPE IN VIEW OF DETECTEDRF ENERGY”, initially filed with the U.S.P.T.O. on the same day as thispatent application, Ser. No. ______, Attorney Docket Number2051.009US1/IMPJ-0155.

The present application may be found to be related to U.S. patentapplication entitled: “ADJUSTING RFID WAVEFORM SHAPE IN VIEW OF SIGNALFROM AN RFID TAG”, initially filed with the U.S.P.T.O. on the same dayas this patent application, Ser. No. ______, Attorney Docket Number2051.013US1/IMPJ-0183.

The present application may be found to be related to U.S. patentapplication entitled: “PERFORMANCE DRIVEN ADJUSTMENT OF RFID WAVEFORMSHAPE”, initially filed with the U.S.P.T.O. on the same day as thispatent application, Ser. No. ______, Attorney Docket Number2051.014US1/IMPJ-0186.

The present application may be found to be related to U.S. patentapplication entitled: “RECONSTRUCTING RFID WAVEFORM SHAPE FOR REUSE ININDIVIDUAL CHANNEL”, initially filed with the U.S.P.T.O. on the same dayas this patent application, Ser. No. ______, Attorney Docket Number2051.015US1/IMPJ-0187.

FIELD

The present disclosure relates to Radio Frequency IDentification (RFID)systems, and more particularly, to apparatus, methods, software, andsystems to improve the performance of RFID systems, for exampleresponsive to the presence of RF energy in communication channels.

BACKGROUND

Radio Frequency IDentification (RFID) systems typically include RFIDtags and RFID readers (the latter are also known as RFID reader/writersor RFID interrogators). RFID systems can be used in many ways forlocating and identifying objects to which the tags are attached. RFIDsystems are particularly useful in product-related and service-relatedindustries for tracking large numbers of objects being processed,inventoried, or handled. In such cases, an RFID tag is usually attachedto an individual item, or to its package.

In principle, RFID techniques entail using an RFID reader to interrogateone or more RFID tags. The reader transmitting a Radio Frequency (RF)wave performs the interrogation. A tag that senses the interrogating RFwave responds by transmitting back another RF wave. The tag generatesthe transmitted back RF wave either originally, or by reflecting back aportion of the interrogating RF wave in a process known as backscatter.Backscatter may take place in a number of ways.

The reflected-back RF wave may further encode data stored internally inthe tag, such as a number. The response is demodulated and decoded bythe reader, which thereby identifies, counts, or otherwise interactswith the associated item. The decoded data can denote a serial number, aprice, a date, a destination, other attribute(s), any combination ofattributes, and so on.

An RFID tag typically includes an antenna system, a power managementsection, a radio section, and frequently a logical section, a memory, orboth. In earlier RFID tags, the power management section included anenergy storage device, such as a battery. RFID tags with an energystorage device are known as active tags. Advances in semiconductortechnology have miniaturized the electronics so much that an RFID tagcan be powered solely by the RF signal it receives. Such RFID tags donot include an energy storage device, and are called passive tags.

A reader algorithm has been described in the prior art, whereby an RFIDreader chooses a channel, and then first listens to see if anotherradio-frequency device is operating in it (“listen-before-talk”). If noother radio-frequency device is operating there, the reader operates inthat channel. If another radio-frequency device is operating in thechannel, the reader moves to a different channel, and again listens, andso on. While this type of algorithm may sometimes be useful in locatingan available channel for communication, improvements are needed for RFIDoperation in the presence of interference and/or noise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of components of an RFID system.

FIG. 2 is a diagram showing components of a passive RFID tag, such as atag that can be used in the system of FIG. 1.

FIG. 3 is a conceptual diagram for explaining a half-duplex mode ofcommunication between the components of the RFID system of FIG. 1.

FIG. 4 is a block diagram of a whole RFID reader system according toembodiments.

FIG. 5 is a block diagram of components of an RFID environment accordingto present embodiments.

FIG. 6A is a flowchart illustrating a method according to presentembodiments.

FIG. 6B is a flowchart illustrating an optional variation of the methodof FIG. 6A.

FIG. 6C is a flowchart illustrating another optional variation of themethod of FIG. 6A.

FIG. 7 illustrates examples of amplitude shift keying (ASK) modulation,and phase reversal amplitude shift keying (PR-ASK) modulation that canbe used for RFID communication.

FIGS. 8A and 8B illustrate example reader system RF-power transmit masksthat can be used for RFID communication.

FIG. 9 illustrates Tari value, pulse width (PW), and data-1 to data-0length ratio relative to signals that can be used for RFIDcommunication.

FIG. 10 illustrates FM0 symbols and FM0 sequences that can be used forRFID communication.

FIG. 11 illustrates FM0 preambles that can be used for RFIDcommunication.

FIG. 12 illustrates possible Miller subcarrier sequences that can beused for RFID communication.

FIG. 13 illustrates possible Miller preambles with and without anadditional pilot tone.

FIG. 14 is a flowchart illustrating a method according to embodiments.

FIG. 15A is a flowchart illustrating a method according to embodiments.

FIG. 15B is a flowchart illustrating an optional variation of the methodof FIG. 15A.

FIG. 15C is a flowchart illustrating another optional variation of themethod of FIG. 15A.

FIG. 16 is a flowchart illustrating a method according to embodiments.

FIG. 17A is a flowchart illustrating a method according to embodiments.

FIG. 17B is a flowchart illustrating an optional variation of the methodof FIG. 17A.

DETAILED DESCRIPTION

Various embodiments of the present invention will be described in detailwith reference to the drawings, where like reference numerals representlike parts and assemblies throughout the several views. Reference tovarious embodiments does not limit the scope of the invention, which islimited only by the scope of the claims attached hereto. Additionally,any examples set forth in this specification are not intended to belimiting and merely set forth some of the many possible embodiments forthe claimed invention.

Throughout the specification and claims, the following terms take atleast the meanings explicitly associated herein, unless the contextclearly dictates otherwise. The meanings identified below are notintended to limit the terms, but merely provide illustrative examplesfor the terms. The meaning of “a,” “an,” and “the” includes pluralreference, the meaning of “in” includes “in” and “on.” The term“connected” means a direct electrical connection between the itemsconnected, without any intermediate devices. The term “coupled” meanseither a direct electrical connection between the items connected or anindirect connection through one or more passive or active intermediarydevices. The term “circuit” means either a single component or amultiplicity of components, either active and/or passive, that arecoupled together to provide a desired function. The term “signal” meansat least one current, voltage, charge, temperature, data, or othermeasurable quantity. The terms “RFID reader” and “RFID tag” are usedinterchangeably with the terms “reader” and “tag”, respectively,throughout the text and claims.

FIG. 1 is a diagram of components of a typical RFID system 100,incorporating aspects of the invention. An RFID reader 110 transmits aninterrogating Radio Frequency (RF) wave 112. RFID tag 120 in thevicinity of RFID reader 110 may sense interrogating RF wave 112, andgenerate wave 126 in response. RFID reader 110 senses and interpretswave 126.

Reader 110 and tag 120 exchange data via wave 112 and wave 126. In asession of such an exchange, each encodes, modulates, and transmits datato the other, and each receives, demodulates, and decodes data from theother. The data is modulated onto, and decoded from, RF waveforms.

Encoding the data in waveforms can be performed in a number of differentways. For example, protocols are devised to communicate in terms ofsymbols, also called RFID symbols. A symbol for communicating can be adelimiter, a calibration symbol, and so on. Further symbols can beimplemented for ultimately exchanging binary data, such as “0” and “1”,if that is desired.

Tag 120 can be a passive tag or an active tag, i.e. having its own powersource. Where tag 120 is a passive tag, it is powered from wave 112.

FIG. 2 is a diagram of an RFID tag 220, which can be the same as tag 120of FIG. 1. Tag 220 is implemented as a passive tag, meaning it does nothave its own power source. Much of what is described in this document,however, applies also to active tags.

Tag 220 is formed on a substantially planar inlay 222, which can be madein many ways known in the art. Tag 220 also includes two antennasegments 227, which are usually flat and attached to inlay 222. Antennasegments 227 are shown here forming a dipole, but many other embodimentsusing any number of antenna segments are possible.

Tag 220 also includes an electrical circuit, which is preferablyimplemented in an integrated circuit (IC) 224. IC 224 is also arrangedon inlay 222, and electrically coupled to antenna segments 227. Only onemethod of coupling is shown, while many are possible.

In operation, a signal is received by antenna segments 227, andcommunicated to IC 224. IC 224 both harvests power, and decides how toreply, if at all. If it has decided to reply, IC 224 modulates thereflectance of antenna segments 227, which generates the backscatterfrom a wave transmitted by the reader. Coupling together and uncouplingantenna segments 227 can modulate the reflectance, as can a variety ofother means.

In the embodiment of FIG. 2, antenna segments 227 are separate from IC224. In other embodiments, antenna segments may alternately be formed onIC 224, and so on.

The components of the RFID system of FIG. 1 may communicate with eachother in any number of modes. One such mode is called full duplex.Another such mode is called half-duplex, and is described below.

FIG. 3 is a conceptual diagram 300 for explaining the half-duplex modeof communication between the components of the RFID system of FIG. 1,especially when tag 120 is implemented as passive tag 220 of FIG. 2. Theexplanation is made with reference to a TIME axis, and also to a humanmetaphor of “talking” and “listening”. The actual technicalimplementations for “talking” and “listening” are now described.

RFID reader 110 and RFID tag 120 talk and listen to each other by takingturns. As seen on axis TIME, when reader 110 talks to tag 120 thecommunication session is designated as “R→T”, and when tag 120 talks toreader 110 the communication session is designated as “T→R”. Along theTIME axis, a sample R→T communication session occurs during a timeinterval 312, and a following sample T→R communication session occursduring a time interval 326. Of course interval 312 is typically of adifferent duration than interval 326—here the durations are shownapproximately equal only for purposes of illustration.

According to blocks 332 and 336, RFID reader 110 talks during interval312, and listens during interval 326. According to blocks 342 and 346,RFID tag 120 listens while reader 110 talks (during interval 312), andtalks while reader 110 listens (during interval 326).

In terms of actual technical behavior, during interval 312, reader 110talks to tag 120 as follows. According to block 352, reader 110transmits wave 112, which was first described in FIG. 1. At the sametime, according to block 362, tag 120 receives wave 112 and processesit. Meanwhile, according to block 372, tag 120 does not backscatter withits antenna, and according to block 382, reader 110 has no wave toreceive from tag 120.

During interval 326, tag 120 talks to reader 110 as follows. Accordingto block 356, reader 110 transmits a Continuous Wave (CW), which can bethought of as a carrier signal that ideally encodes no information. Asdiscussed before, this carrier signal serves both to be harvested by tag120 for its own internal power needs, and also as a wave that tag 120can backscatter. Indeed, during interval 326, according to block 366,tag 120 does not receive a signal for processing. Instead, according toblock 376, tag 120 modulates the CW emitted according to block 356, soas to generate backscatter wave 126. Concurrently, according to block386, reader 110 receives backscatter wave 126 and processes it.

In the above, an RFID reader/interrogator may communicate with one ormore RFID tags in any number of ways. Some such ways are calledprotocols. A protocol is a specification that calls for specific mannersof signaling between the reader and the tags.

One such protocol is called the Specification for RFID AirInterface-EPC™ Radio-Frequency Identity Protocols Class-1 Generation-2UHF RFID Protocol for Communications at 860 MHz-960 MHz, which is alsocolloquially known as “the Gen2 Spec”. The Gen2 Spec has been ratifiedby EPCglobal, which is an organization that maintains a website at:<http://www.epcglobalinc.org/> at the time this document is initiallyfiled with the USPTO.

It was described above how reader 110 and tag 120 communicate in termsof time. In addition, communications between reader 110 and tag 120 maybe restricted according to frequency. One such restriction is that theavailable frequency spectrum may be partitioned into divisions that arecalled channels. Different partitioning manners may be specified bydifferent regulatory jurisdictions and authorities (e.g. FCC in NorthAmerica, CEPT in Europe, etc.).

The reader 110 typically transmits with a transmission spectrum thatlies within one channel. In some regulatory jurisdictions theauthorities permit aggregating multiple channels into one or more largerchannels, but for all practical purposes an aggregate channel can againbe considered a single, albeit larger, individual channel.

Tag 120 can respond with a backscatter that is modulated directly ontothe frequency of the reader's emitted CW, also called basebandbackscatter. Alternatively, Tag 120 can respond with a backscatter thatis modulated onto a frequency, developed by Tag 120, that is differentfrom the reader's emitter CW, and this modulated tag frequency is thenimpressed upon the reader's emitted CW. This second type of backscatteris called subcarrier backscatter. The subcarrier frequency can be withinthe reader's channel, can straddle the boundaries with the adjacentchannel, or can be wholly outside the reader's channel.

A number of jurisdictions require a reader to hop to a new channel on aregular basis. When a reader hops to a new channel, it may encounter RFenergy that could interfere with communications in it.

Embodiments of the present disclosure can be useful in different RFIDenvironments, for example, in the deployment of RFID readers in sparse-or dense-reader environments, in environments with networked anddisconnected readers such as where a hand-held reader may enter thefield of networked readers, in environments with mobile readers, or inenvironments with other interference sources. It will be understood thatthe present embodiments are not limited to operation in the aboveenvironments, but may provide improved operation in such environments.

FIG. 4 is a block diagram of a whole RFID reader system 400 according toembodiments. System 400 includes a local block 410, and optionallyremote components 470. Local block 410 and remote components 470 can beimplemented in any number of ways. It will be recognized that reader 110of FIG. 1 is the same as local block 410, if remote components 470 arenot provided. Alternately, reader 110 can be implemented instead bysystem 400, of which only the local block 410 is shown in FIG. 1.

Local block 410 is responsible for communicating with the tags. Localblock 410 includes a block 451 of an antenna and a driver of the antennafor communicating with the tags. Some readers, like that shown in localblock 410, contain a single antenna and driver. Some readers containmultiple antennas and drivers and a method to switch signals among them,including sometimes using different antennas for transmitting and forreceiving. And some readers contain multiple antennas and drivers thatcan operate simultaneously. A demodulator/decoder block 453 demodulatesand decodes backscattered waves received from the tags via antenna block451. Modulator/encoder block 454 encodes and modulates an RF wave thatis to be transmitted to the tags via antenna block 451.

Local block 410 additionally includes an optional local processor 456.Processor 456 may be implemented in any number of ways known in the art.Such ways include, by way of examples and not of limitation, digitaland/or analog processors such as microprocessors and digital-signalprocessors (DSPs); controllers such as microcontrollers; softwarerunning in a machine such as a general purpose computer; programmablecircuits such as Field Programmable Gate Arrays (FPGAs),Field-Programmable Analog Arrays (FPAAs), Programmable Logic Devices(PLDs), and any combination of one or more of these; and so on. In somecases the decoding function in block 453, the encoding function in block454, or both may be performed instead by processor 456.

Local block 410 additionally includes an optional local memory 457.Memory 457 may be implemented in any number of ways known in the art.Such ways include, by way of examples and not of limitation, nonvolatilememories (NVM), read-only memories (ROM), random access memories (RAM),any combination of one or more of these, and so on. Memory 457, ifprovided, can include programs for processor 456 to run, if provided.

In some embodiments, memory 457 stores data read from tags, or data tobe written to tags, such as Electronic Product Codes (EPCs), TagIdentifiers (TIDs) and other data. Memory 457 can also include referencedata that is to be compared to the EPC codes, instructions and/or rulesfor how to encode commands for the tags, modes for controlling antenna451, and so on. In some of these embodiments, local memory 457 isprovided as a database.

Some components of local block 410 typically treat the data as analog,such as the antenna/driver block 451. Other components such as memory457 typically treat the data as digital. At some point there is aconversion between analog and digital. Based on where this conversionoccurs, a whole reader may be characterized as “analog” or “digital”,but most readers contain a mix of analog and digital functionality.

If remote components 470 are indeed provided, they are coupled to localblock 410 via an electronic communications network 480. Network 480 canbe a Local Area Network (LAN), a Metropolitan Area Network (MAN), a WideArea Network (WAN), a network of networks such as the internet, and soon. In turn, local block 410 then includes a local network connection459 for communicating with network 480.

There can be one or more remote component(s) 470. If more than one, theycan be located at the same place with each other, or in differentplaces. They can access each other and local block 410 via network 480,or via other similar networks, and so on. Accordingly, remotecomponent(s) 470 can use respective remote network connections. Only onesuch remote network connection 479 is shown, which is similar to localnetwork connection 459, etc.

Remote component(s) 470 can also include a remote processor 476.Processor 476 can be made in any way known in the art, such as wasdescribed with reference to local processor 456.

Remote component(s) 470 can also include a remote memory 477. Memory 477can be made in any way known in the art, such as was described withreference to local memory 457. Memory 477 may include a local database,and a different database of a Standards Organization, such as one thatcan reference EPCs.

Of the above-described elements, it is advantageous to consideroperational processing block 490. Block 490 includes those that areprovided of the following: local processor 456, remote processor 476,local network connection 459, remote network connection 479, and byextension an applicable portion of network 480 that links connection 459with connection 479. The portion can be dynamically changeable, etc. Inaddition, block 490 can decode RF waves received via antenna 451, andcause antenna 451 to transmit RF waves according to what it hasprocessed. It can even be said that block 490 can receive RF waves, inwhich case it is meant that block 490 can receive data about the waves,and so on.

Block 490 includes either local processor 456, or remote processor 476,or both. If both are provided, remote processor 476 can be made suchthat it operates in a way complementary with that of local processor456. In fact, the two can cooperate. It will be appreciated that block490, as defined this way, is in communication with both local memory 457and remote memory 477, if both are present.

Accordingly, block 490 is location agnostic, in that its functions canbe implemented either by local processor 456, or by remote processor476, or by a combination of both. Some of these functions are preferablyimplemented by local processor 456, and some by remote processor 476.Block 490 accesses local memory 457, or remote memory 477, or both forstoring and/or retrieving data.

Block 490, along with all of the circuits described in this document maybe implemented as circuits in the traditional sense. All or some of themcan also be implemented equivalently by other ways known in the art,such as by using one or more processors, DSPs, FPGAs, FPAAs, PLDs,combination of hardware and software, etc.

Reader system 400 operates by block 490 generating communications forRFID tags. These communications are ultimately transmitted by antennablock 451, with modulator/encoder block 454 encoding and modulating theinformation on an RF wave. Then data is received from the tags viaantenna block 451, demodulated and decoded by demodulator/decoder block453, and processed by processing block 490.

Embodiments of the disclosure provide an RFID reader that is capable ofthe methods described below. In some embodiments software is providedfor controlling an RFID reader that operates as per the describedmethods. The software is not limed to physical locations and can beimplemented as a standalone module or as a collection of cooperatingdistributed modules. The described embodiments may be performed in manyways, including by devices that can perform the described methods. Suchdevices can be implemented in many ways, as will be obvious to a personskilled in the art in view of the present description.

The operations of this description, such as those of block 490, may beimplemented by one or more devices that include logic circuitry. Thedevice(s) perform functions and/or implement methods as described inthis document. The device(s) may include a processor that may beprogrammable for a general purpose, and/or may include a dedicatedelement or elements such as a microcontroller, microprocessor, DSP, etc.For example, the device(s) may be a digital-computer-like element, suchas a general-purpose computer selectively activated or reconfigured by acomputer program stored in the computer or in its memory. Alternately,the device may be implemented by an FPGA, FPAA, PLD, ApplicationSpecific Integrated Circuit (ASIC), etc.

Moreover, methods are described below. The methods and algorithmspresented herein need not be associated with any particular computer orother apparatus. Rather, various general-purpose machines may be usedwith programs in accordance with the teachings herein, or it may provemore convenient to construct more specialized apparatus to perform therequired method steps. The required structure for a variety of thesemachines will become apparent from this description.

In all cases there should be borne in mind the distinction betweenmethods provided in this description, and methods of operating acomputing machine. This description relates both to methods in general,and also to methods for operating a computing machine for processingelectrical or other such physical signals to generate other desiredphysical signals.

Programs are additionally included in this description, as are methodsof operation of the programs. A program is generally defined as a groupof steps leading to a desired result, due to the nature of the elementsin the steps and their sequence. A program is usually advantageouslyimplemented as a sequence of steps for a computing machine, such as ageneral-purpose computer, a special-purpose computer, a microprocessor,etc.

Storage media are additionally included in this description. Such media,individually or in combination with others, have stored thereoninstructions of a program made according to the invention. A storagemedium according to the invention is a computer-readable medium, such asa memory, and is read by the computing machine mentioned above.

Performing the steps or instructions of a program requires manipulationof physical quantities. Usually, though not necessarily, thesequantities may be transferred, combined, compared, and otherwisemanipulated or processed according to the steps or instructions, andthey may also be stored in a computer-readable medium. These quantitiesinclude, for example, electrical, magnetic, and electromagnetic chargesor particles, states of matter, and in the more general case can includethe states of any physical devices or elements. It is convenient attimes, principally for reasons of common usage, to refer to informationrepresented by the states of these quantities as bits, data bits,samples, values, symbols, characters, terms, numbers, or the like. Itshould be borne in mind, however, that all of these and similar termsare associated with the appropriate physical quantities, and that theseterms are merely convenient labels applied to these physical quantities,individually or in groups.

This detailed description is presented largely in terms of flowcharts,algorithms, and symbolic representations of operations on data bits onand/or within at least one medium that allows computational operations,such as a computer with memory. Indeed, such descriptions andrepresentations are the type of convenient labels used by those skilledin programming and/or the data processing arts to effectively convey thesubstance of their work to others skilled in the art. A person skilledin the art of programming may use these descriptions to readily generatespecific instructions for implementing a program according to thepresent invention.

Often, for the sake of convenience only, it is desirable to implementand describe a program as various interconnected distinct softwaremodules or features, individually and collectively also known assoftware. This is not necessary, however, and there may be cases wheremodules are equivalently aggregated into a single program with unclearboundaries. Furthermore, one or more modules may be advantageouslyimplemented in a logic device such as an FPGA, FPAA, PLD, ASIC, and thelike. In any event, the modules or features of this description may beimplemented by themselves, or in combination with others. Even though itis said that the program may be stored in a computer-readable medium, itshould be clear to a person skilled in the art that it need not be asingle memory, or even a single machine. Various portions, modules orfeatures of it may reside in separate memories, or even separatemachines. The separate machines may be connected directly, or through anetwork such as a local access network (LAN) or a global network such asthe Internet.

It will be appreciated that some of these methods may include softwaresteps which may be performed by different modules of an overall part ofa software architecture. For example, wave shaping in a reader may beperformed in a data plane, which consults a local wave-shaping table.Collecting performance data may also be performed in a data plane. Theperformance data may be processed in a control plane, which accordinglymay update the local wave-shaping table, in addition to neighboringones. A person skilled in the art will discern which step is bestperformed in which plane.

An economy is achieved in the present document in that a single set offlowcharts is used to describe both programs and methods. So, whileflowcharts are described in terms of boxes, they can mean both programsand methods.

For this description, the methods may be implemented by machineoperations. In other words, embodiments of programs, which may beimplemented by machine operations, are made such that they performmethods of the invention described in this document. These machineoperations may be optionally performed in conjunction with one or morehuman operators performing some, but not all of them. As per the above,the human operators need not be collocated with each other, but eachonly with a machine that performs a portion of the program. Alternately,some of these machines may operate automatically, without humanoperators and/or independently from each other.

FIG. 5 is a block diagram of an RFID system and representative operatingenvironment. An RFID reader 510 includes antenna(s) 520 for transmissionand reception of RFID signals, as described above. A transmission module522 is provided to transmit signals from the reader via antenna(s) 520.

RFID reader 510 also includes a reception/energy detection module 524.Module 524 can receive signals and detect energy encountered inconjunction with the received signals. The operations ofreception/energy detection can be performed at Radio Frequencies (RF),after frequency downconversion, or after frequency upconversion(collectively “frequency conversion”).

RFID reader 510 moreover includes an RF channel selector module 526,provided with antenna(s) 520 to select a channel for operation, i.e. fortransmitting and/or receiving signals.

RFID reader 510 additionally includes a waveform shaping parameteradjust module 530, as explained in more detail in this document. Module530 can adjust one or more waveform shaping parameters of either or boththe signals transmitted by reader 510, and the backscattered signalsreceived from, RFID tags 550. Examples of waveform shaping parametersare given later in this document.

It will be appreciated that one or more of modules 524, 526 and 530 canbe implemented by one or more elements of operational processing block490, typically but not necessarily in conjunction withdemodulator/decoder 453 and modulator/encoder 454.

A separate energy detector module 580 can optionally be provided todetect RF energy present in the operating environment of the reader 510.Module 580 can be a standalone module or can be implemented by remoteprocessor 476. Module 580 can detect signals or energy at RF, afterfrequency conversion, or both. In operation, module 580 alone, orreception/energy detection module 524 alone, or a combination of bothmodules, detect RF energy or signals present in the operatingenvironment of a reader or readers. Module 580 can monitor the operatingenvironment for use by one reader, or for use by multiple readers.Multiple energy detection modules 580 can be dedicated to multiplechannels, operating concurrently. Or a single energy detection module580 can listen to channels one at a time, e.g. in rotation. Further, amodule 580 can listen to a combination of channels, e.g. all at once,and infer about each particular one. The energy detection modules 524and 580 can monitor the operating environment continuously, or atpredetermined intervals, or when certain trigger events happen, such asbut not limited to when reader performance degrades relative to athreshold, when told to, etc.

It will be understood that the term Signal refers to the desiredcommunication signals between a reader and tag(s). Noise means undesiredand indecipherable RF energy such as thermal noise, shot noise, andother noise-like energy. Interference means signals from other RFdevices and from other non-RF devices that happen to be emitting RFenergy, even in communicating with each other. A Signal-to-Noise Ratio(SNR) is defined as the power in the signal divided by the power in thenoise. A Signal-to-Noise-and-Interference Ratio (SINR) is defined as thepower in the signal divided by the powers in the noise plus the power inthe interference.

The RF energy that is detected can originate from a plethora ofdifferent sources, including but not limited to other RFID readers 560and other RF devices 570, across the air interface. The energy caninclude modulated signals, unmodulated signals, decodable signals,undecodable signals, RF noise, interference, or a mixture thereof. Theother RF devices can include devices used in industry, such as motors,that are not intended to operate as RF devices but create RFinterference or noise.

As referred to later in this document, detecting RF energy can bedetecting signal, detecting noise, detecting interference, detectingsignal and/or noise and/or interference, receiving information about thesignal and/or noise and/or interference, or inferring the signal and/ornoise and/or interference from operational performance parameters suchas tag read rate. The RF energy may be detected as an average power, asa peak power, as an integrated power, as a power spectral density (PSD)(for example, a Fast Fourier Transform (FFT) effectively computes aPSD), etc.

As stated above, the waveform shaping parameter module 530 adjustswaveform shaping parameters based upon energy encountered in theoperational RF environment of the reader 510. Embodiments are nowdescribed, of the type of energy, waveform shaping options, andprocessing techniques.

FIG. 6A is a flowchart 600 illustrating methods for reader systems ofthe present disclosure, such as to communicate with RFID tags. Theindividual operations of the methods of flowchart 600 can be implementedin many different ways, as will be understood by a person skilled in theart. In addition, they can be implemented by the physical componentsdescribed earlier in this document.

According to an operation 610, a first channel is selected out of anumber of them in a spectrum. This selection can be performed forexample by RF channel selector 526. The selection can be associated withparameters or flags being set in software, or switches moving inhardware, and the like. These may adjust the antenna to operate at acertain channel.

According to another operation 620, RF energy is detected. As statedabove, the energy can be detected using energy detector module 580 orenergy detection module 524, or a combination of the two modules.Equivalently, instead of energy being detected, an input is receivedconveying a value for the detected energy.

In some embodiments, the RF energy is detected prior to selecting thefirst communication channel at operation 610. It can even be detectedprior to subdividing the available frequency spectrum into channels inthe first place. This subdivision, also known as channelization, cantake place in response to the RF energy detected in the spectrum. Forexample, the channel width can depend on the amount of ambient noise,etc. Even after channelization, the RF energy can be detected in aplurality of channels simultaneously, in individual channelssequentially, or any combination thereof, and the first channel can beselected from the plurality of channels responsive to the detection andpossibly measurement.

In some embodiments, the energy in operation 620 is detected afterchannelization, and thus after the first channel has been defined, andafter the first channel has been selected per operation 610. In some ofthose, the detected energy in operation 620 is of the type typicallyencountered in conjunction with using the selected first channel. Forexample, it can be the RF energy presently in the selected firstchannel. In some of these embodiments, the RF energy can include energyin any other related channels, such as in adjacent channels, where tagscould be backscattering, responding to a reader's signal in the firstchannel. Accordingly, the detected RF energy can include noise, signalsthat are decodable, interference from any source in the environment,etc. In some embodiments, it can also include energy resulting from thereader system's own operation, such as reflected by fluorescent lightsources, etc.

In some embodiments, a level of the detected RF energy is measured, toyield a value. The value can have units, such as dB. Or the value canhave units assigned based on possible ranges of the value, such aslow/medium/high, or low/high, digital values such as 0/1, and so on. Ifthe detected RF energy includes noise, the units can be values such as“quiet”/“noisy”, etc.

In some embodiments, the detected RF energy includes a signal, which isfurther demodulated and/or decoded prior to measurement. More exampleswill be presented later in this document.

According to operation 630, a waveform shaping parameter is adjustedresponsive to the detected RF energy. This waveform shaping parameter isalso called the own waveform shaping parameter, in that it is aparameter of a system, device, software, or method according toembodiments, as distinguished from other waveform shaping parametersthat can be determined, for example by detecting, decoding andinterpreting signals from other readers or tags. A great value,therefore, of the invention is where operation must be in an environmentwhere other readers already operate. Such scenarios were explained inmore detail in copending U.S. application Ser. No. 11/195,468 filed onAug. 1, 2005, entitled “PREVENTING COMMUNICATION CONFLICT WITH OTHERRFID READERS”.

Adjusting the own waveform shaping parameter can be performed in anumber of ways, some of which are described below. Most of these waysinvolve decisions and settings within software and hardwarerespectively, such as setting flags and configuring circuits to operatein certain ways, and so on. In quite a number of these embodiments,features of the detected RF energy are identified, values for thesefeatures are determined, etc., and the own waveform shaping parameter isadjusted in view of these features, values, etc. These features caninclude the level of the detected RF energy, and others as will beespecially evident from the below. Optionally, additional own waveformshaping parameters can further be adjusted, and so on.

According to operation 640, first RF waves are transmitted to the RFIDtags in the selected channel, which can be the first channel or anotherchannel selected in the meantime instead of the first channel.

According to an optional operation 650, second RF waves are received,which are backscattered from the RFID tags in response to thetransmitted first RF waves. The second RF waves can be within the samechannel, or other nearby channels.

Either the first RF waves of operation 640, or the second RF waves ofoperation 650, or both, have a waveform with a shape according to theadjusted waveform shaping parameter(s).

Here the designations “first” and “second”, and later “third” and“fourth” are given for convenience, and do not, by themselves alone,imply a chronological order. Such an order can, however, be inferredfrom causation, for example when second waves are backscatteredresponsive to first waves, etc.

In other embodiments, the above described operations can be performed incombination with other operations, or in different order.

For example, operation 640 typically takes place after operation 620,although that is not necessary. Other orders are also possible.

For another example, third RF waves can be transmitted to the RFID tagsprior to adjusting the waveform shaping parameter, either in theselected channel or otherwise, and even before the first waves. The RFenergy can be detected before or after transmitting the third waves.

Even more, fourth waves may be received from the tags in response to thethird waves, and even before the first waves. The RF energy can bedetected before or after receiving the fourth waves.

FIG. 6B illustrates a flowchart 660 of embodiments of flowchart 600, formethods to apply a rule to the detected RF energy. Operations 620 and630 are shown again, from flowchart 600.

In addition, according to operation 665, a rule is applied to thedetected RF energy. The rule can be applied by implementing a table, aformula, an algorithm, etc. Further, the rule can be updated duringoperation, for example by updating either the whole rule, or merelyparameters of it such as table entries, formula coefficients, and thelike.

A result is determined from applying the rule. The waveform shapingparameter can therefore be adjusted according to the result.

FIG. 6C illustrates a flowchart 670 of embodiments with furtherextensions of the method with flowchart 600. Flowchart 670 includesoperations 610, 620, 630, 640 and 650 of flowchart 600.

According to an additional operation 672, a second communication channelis selected, after the first channel has been selected in operation 610.In some embodiments, operation 672 takes place before any transmissionhas occurred, such as at operation 640. In other embodiments, operation672 takes place after such transmission has occurred.

According to a next operation 674, RF energy is detected, such as of thetype encountered in conjunction with using the second channel, which isnow selected.

According to a next operation 676, the detected RF energies arecompared. If, as is preferred, values have been assigned, then thevalues are compared.

According to a next operation 678, the first or the second channel isselected, depending on the comparison of operation 676. Preferably, theselection is made so that the impending transmission in the selectedchannel and reception would be the most likely to succeed. Metrics canbe used, so that the impending transmission will have the best SNR orSINR.

Then operation 630 takes place as explained above, and also in view ofthe comparison of operation 676 and/or the selection of operation 678.

Then operations 640 and 650 take place as explained above. The selectedchannel of operation 640 could now be the second channel instead of thefirst channel.

Waveform shaping parameters are now described in more detail.

Such parameters represent how the waveform of RF waves is shaped,whether it is a reader-to-tag (R→T) transmission, or for tag-to-reader(T→R) backscattered transmission. Indeed, the waveform can be shapedevery time any information is encoded in it. An example can be seen bybriefly consulting FIG. 7 and FIG. 9, where a waveform has asubstantially constant nominal maximum amplitude, and information isencoded by low-going pulses from that amplitude than a nominal maximumamplitude. The nominal maximum amplitude can further be taken as acontinuous wave, and can be set or changed according to yet otherconsiderations.

These waveform shaping parameters are settable. It will be appreciatedthat those parameters are set by the reader; in other words, readerscontrol in part how the tags are to behave.

Settable parameters are now described in more detail.

Some of these waveform shaping parameters control a choice of a protocolof communication, for the RFID reader and the RFID tag. For example,when a tag is capable of communicating in two or more differentprotocols, the waveform shaping parameter can dictate the encoding ofthe reader wave, so that the receiving tag will understand whichprotocol is designated.

One settable parameter is the reader's allowed operating frequency orfrequencies, which are typically required to be within a frequency rangedictated by regulatory rules.

Another settable parameter is frequency diversity. As one example offrequency diversity, RFID readers may choose to, or may be required to,‘hop’ at regular intervals among multiple frequencies in the allowedrange. Such readers are often called “frequency hopping” readers. Anexample of readers that do not use frequency diversity is readers thattransmit at a chosen frequency in the allowed range, typically notchanging frequency unless there is a reason to do so.

Some of the waveform shaping parameters control a choice of a modulationformat, i.e. the format by which readers transmit, or tags are tobackscatter. Possibilities for the latter include double-sidebandamplitude shift keying (DSB-ASK), single-sideband ASK (SSB-ASK),phase-reversal ASK (PR-ASK), and PSK (phase shift keying). Othermodulation formats are possible as well.

FIG. 7 illustrates two of the above mentioned modulation formats. One ofthem is a signal using ASK modulation, and the other is a signal usingPR-ASK modulation. Other modulation formats are possible.

Yet other settable parameters relate to the RF spectrum used, and powerlevel. For example, different transmission spectral masks allow forconstraining different amounts of out-of-channel or out-of-band spectralenergy. A reader may be constructed to meet one transmission spectralmask under some operating conditions, and another mask for differentoperating conditions. Two sample transmit spectral masks are shown.

FIG. 8A shows a mask referenced to channels, whereas FIG. 8B shows amask referenced to Tari values. Other masks are also possible.

Some of the waveform shaping parameters control a choice of a signalencoding. These include one or a combination of: a data rate; a pulsedepth; a pulse rise time; a pulse fall time; a pulse width; a Tarivalue; a data-1 to data-0 length ratio (for signaling that usespulse-interval encoding (PIE)); PIE ratio; TRcal pulse; RTcal pulse; ashaping of the pulses, such as sinusoidal or square-wave shaped pulses;a line code; and a preamble. Some of these can be communicated byspecial attributes of one or more calibration pulses. An example is nowgiven.

FIG. 9 shows an example for R→T signaling that uses PIE, after a wavesuch as that of FIG. 7 has been converted by tag electronics. In thiscase, the durations between high→low and low→high transitions conveyinformation. The Tari value is the length of a data zero, the PW is thewidth of the low pulse, and the ratio of a data-1 length to a data-0length, such as in the range 1.5:1 to 2:1.

T→R symbols are typically encoded using a variety of line codes. Twosuch types of line codes are FM0 and Miller encoding, both of which arewell known in the art.

FIG. 10 illustrates FM0 symbols and two-bit FM0 sequences. In FM0encoding, a transition is required at the end of each symbol period;additionally, for a zero bit, an additional transition is required inthe middle of a symbol.

Tag backscatter typically begins with a transmitted preamble. Some ofthe waveform shaping parameters control a choice of a preamble. A readermay send a command, such as a Query command, from reader to a tag, whichtells the tag which preamble to use, e.g. by setting a TRext variable. Anumber of preambles are possible.

FIG. 11 shows two possible preambles, a short preamble (TRext=0) or along preamble (TRext=1). As explained herein, a reader may request tagsto use longer or more robust preambles (such as is illustrated forTRext=1) in noisy environments, to aid in preamble detection by thereader.

In Miller encoding, a transition occurs between two data zeros insequence, and also in the middle of a data one. In one embodiment, aMiller symbol can contain 2, 4 or 8 subcarrier cycles for eachtransmitted bit.

FIG. 12 illustrates some possible Miller subcarrier sequences. Thesymbol period is the length of a data bit (period between dashed lines).The subcarrier frequency is the frequency of the underlying waveform. Mis the number of subcarrier cycles per symbol. As described above, oneparameter in the T→R signal encoding is the choice of line code. If theline code permits subcarriers, additional parameters include thesubcarrier frequency and the number of subcarrier cycles per symbol.

FIG. 13 shows how a Miller message from T→R can be constructed to beginwith a preamble. A short preamble (TRext=0) or a long preamble (TRext=1)can be used. Other preambles are possible as well. As per the above, areader may request tags to use a longer or more robust preamble in noisyenvironments, to aid in preamble detection by the reader.

In further embodiments, the waveform shaping parameter represents aprotocol parameter for RFID system 100 to operate according to acommunications protocol. The protocol parameter can be one, or acombination of commands, data, tag operating parameters for how tags areto operate, and the like specified by the protocol. For example, acommand can be for a tag to change its state machine, or to respond in acertain manner according to the protocol. Responding can be by giving anacknowledgement (ACK), a handle such as a random number (RN), a tag codesuch as an EPC, etc. Or the protocol parameter can dictate anerror-detection and/or correction method; a security method; a messagetruncation; whether the tags respond using a baseband frequency of theCW waves or a subcarrier frequency of the CW waves; parameters as to howto respond as per the above; filtering; frequency-tracking method;inventorying session identifying number; and the like.

In further embodiments, the waveform shaping parameter controls a choiceof a parameter for RFID system 100 to operate under a protocol. Theparameter can be one, or a combination of: an inventorying sessionidentifying number; a state-change instruction to a tag; anerror-detection and/or correction method; a security method; a messagetruncation; whether the tags respond using a baseband frequency of theCW waves or a subcarrier frequency of the CW waves; parameters forcontrolling how an RFID tag adjusts its state, generates a randomnumber, and replies to a reader; filtering; and a frequency-trackingmethod.

The choices made in R→T and T→R signal encoding or protocol operationcan cause the data transmissions to be more or less robust, typicallyslowing down or accelerating data transmission, respectively. As anexample, protocol operation can add error correction to the tagbackscatter, slowing down message transmission but also increasing theprobability that a received message is decoded properly by the reader.

FIG. 14 is a flowchart 1400 for illustrating methods according tofurther embodiments. The methods of flowchart 1400 are for adjusting anRFID waveform shaping parameter in view of signals from another RFIDreader in the channel, and can be performed by the elements describedabove. The methods of flowchart 1400 include operations 610, 640 and650, which have already been described.

According to an operation 1420, RF energy is detected within theselected channel. This may be performed similarly with how operation 620is performed, except that RF energy need be detected only within theselected channel, not any of the related ones.

According to an operation 1422, the detected RF energy is identified asa reader system signal, such as from another RFID reader system. Thiscan be performed by identifying characteristics of the detected RFenergy, such as intensity, types of modulation, and the like.

According to an optional next operation 1424, the identified readersystem signal is decoded. Decoding can take place in a number of ways,for example by checking whether a protocol of communication is beingadhered to, and then decoding according to the protocol. This can beperformed by functionality that can decode reader signals, provided inaddition to the above mentioned functionality for decoding backscatteredtag signals.

In some embodiments, the identification of operation 1422 can beperformed as a result of the decoding of operation 1424, and thereforewith their order interchanged. Indeed, decoding operation 1424 canstart, and if it works for a reader signal, it can be inferred that theenergy detected at operation 1420 was indeed a reader signal, hence theidentification of operation 1422.

According to an optional operation 1426, an other waveform shapingparameter is interpreted from the reader system signal decoded atoperation 1424. The other waveform shaping parameter is distinguishablefrom the own waveform shaping parameter as per the above, but it can bethe same type of parameter or parameters.

According to an operation 1430, the own waveform shaping parameter isadjusted. This takes place similarly to the previously describedoperation 630, but this time in view of the reader system signal decodedat operation 1424. If optional operation 1426 has also taken place, thenthe own waveform shaping parameter can be adjusted also in view of theinterpreted other waveform shaping parameter.

Then operations 640 and 650 take place as described previously.

In a number of embodiments, RFID readers query RFID tags in what iscalled an inventorying session. A reader sends to the tag a Querycommand containing a parameter Q. Each tag generates a random number inthe range from zero to 2^(Q)−1, and any tag that generates a zeroreplies to the reader. If the reader observes a single tag replying inresponse to the Query, it acknowledges the single tag by transmitting anACK command. This method of uniquely identifying RFID tags is a variantof the well-known slotted-Aloha collision-arbitration algorithm, and isparticularly well suited for use in RFID systems.

To maximize the probability that a single tag, among all the tags in thefield, will eventually generate a zero, the reader should choose Q suchthat 2^(Q)−1 is approximately equal to the number of tags in the field,as described in copending published U.S. patent application2005/0280507, Ser. No. 11/210,573, filed on Aug. 24, 2005 and titled:“INVENTORYING RFID TAGS BY EMPLOYING A QUERY PARAMETER Q THAT CONVERGESHEURISTICALLY”.

In these embodiments, the other waveform shaping parameter includes aninterpreted Q parameter suitable for controlling how an RFID taggenerates a random number during an inventorying session. In thoseembodiments, the own waveform shaping parameter encodes a transmitted Qparameter whose value is determined from a value of the interpreted Qparameter.

The value of the transmitted Q parameter can be determined in any numberof ways. It can be equal to that of the interpreted Q parameter. Or itcan be a statistic of a number of interpreted Q parameter, such as amean.

A R→T waveform shaping parameter can encode a tag operating parameter,such as the Q parameter, that controls how an RFID tag generates arandom number. In one embodiment of the present invention a Q parameter,decoded from another RFID reader 560, can be advantageously used toadjust a waveform shaping parameter of reader 510. For example, thedecoded Q parameter from reader 560 can be used to adjust a Q parameterof reader 510. In one embodiment, the encoded Q parameter of reader 510starts at a value equal to the Q parameter decoded from reader orreaders 560. Further, multiple decoded commands from a reader or readers560 can yield a plurality of decoded Q parameters, and the encoded Qparameter of reader 510 can start at a value equal to a mean value ofthe plurality of decoded Q parameters.

In yet another embodiment, in the decoded signal from the other readeror readers 560, a Query Command is not followed by an ACK command, inwhich case the encoded Q parameter of reader 510 is set to zero.

The following examples help explain the above-mentioned responses todecoded signals from another reader or readers 560. In response to otherreaders 560 sending Query commands with Q=0, a judgment is made thatthere may be few or no tags in the field and reader 510 starts aninventory round with a wave-shaping parameter encoding Q=0.

In response to other readers 560 sending Query commands with Q valuesranging from 0 to 4, a judgment is made that there may be at most2⁴−1=15 tags in the field, and reader 510 starts an inventory round witha wave-shaping parameter encoding Q=4.

In response to other readers 560 sending Query commands with widelydifferent Q values, a judgment is made that there are an unknown numberof tags in the field, and reader 510 starts an inventory round with Qset to the mean of the observed values the other readers 560 are using.

In response to other readers 560 sending Query commands but no ACKcommands, a judgment is made that there may be few or no tags in thefield and reader 510 starts an inventory round with Q=0, so the firstpowered tag will always generate a random number equal to 2⁰−1=0 andwill reply without delay.

In response to another reader 560 sending a Write command, a judgment ismade that the other reader is performing a difficult/sensitive operationthat should not be interrupted, and reader 510 avoids transmitting.Alternatively, reader 510 can use a narrow transmit bandwidth and lowtransmit power to avoid interrupting reader 560 that is sending theWrite command.

In response to other readers 560 sending Query commands and no ACKcommands, but reader 510 is seeing many tags, a judgment is made byreader 510 to aggregate multiple channels and use the aggregated channelfor transmissions. Reader 510 may make this decision because the otherreaders 560 are not seeing any tags so they are less susceptible tointerference, whereas reader 510 needs extra signal bandwidth toincrease its communication rate and inventory all the tags.

In response to other readers 560 using low values of Q, a judgment ismade that there are few tags in the field and reader 510 can transmitintermittently rather than continuously.

In response to other readers 560 using high values of Q, a judgment ismade that there are many tags in the field and reader 510 can transmitcontinuously rather than intermittently.

In response to detected signals from a reader or readers 560 having areceived power level or levels below an interference threshold, ajudgment is made that the other reader or readers 560 are far away, sothe tag subcarrier backscatter frequency can be placed in a differentchannel from the reader 510 transmissions without risk of interferencefrom other readers 560.

In response to other readers operating using R→T and T→R communicationparameters (i.e. Tari, backscatter data rate, etc.) consistent withdensely populated reader environments (hereinafter “dense-reader mode”),a judgment is made by reader 510 that the environment is denselypopulated with readers 560, so reader 510 uses a dense-reader mode. Inresponse to other readers 560 using a dense-reader mode, but theirreceived power at reader 510's antenna is low, a judgment is made byreader 510 that the environment is densely populated with readers 560,but they are not nearby. As such, reader 510 can use a non-dense-readermode.

In response to other readers 560 using a dense-reader mode, but, basedon the observed channel occupancy there are few readers 560 actuallytransmitting, a judgment is made by reader 510 that the environment mayhave been densely populated with readers 560 but some of them haveturned off. Reader 510 can then use a non-dense-reader mode rather thana dense-reader mode. If the other readers 560 subsequently transition toa non-dense-reader mode, then reader 510 can stay in a non-dense-readermode. If the other readers 560 stay in a dense-reader mode, then theymust be experiencing interference issues, so reader 510 can switch to adense-reader mode.

In response to other readers 560 issuing Select commands, such that onlytags that are applied to specific products will reply, a judgment ismade that there is a priority in finding tags on such specific productsand reader 510 can then report the identification of such tags with highpriority.

In some embodiments the RF energy encountered may be signals from tags550 communicating with other readers 560. These signals are decodableand can be used by reader 510 to adjust waveform shaping parameters.

FIG. 15A is a flowchart 1500 for illustrating methods according tofurther embodiments. The methods of flowchart 1500 are for adjusting anRFID waveform shaping parameter in view of detected RFID tag signals,and can be performed by the elements described above. The methods offlowchart 1500 include operations 610, 640 and 650 already describedabove.

According to an operation 1520, fourth RF waves are detected andreceived in the selected channel. This may be performed similarly withhow operation 620 is performed, except that only the selected channel ismonitored.

According to a next operation 1522, the received fourth RF waves areidentified as backscatter from RFID tags, which happen to be in thefield of view. This can be performed by identifying characteristics ofthe received fourth RF waves, such as intensity, types of modulation,and the like.

According to a next operation 1524, the identified tag backscatter isdecoded. Decoding can take place in a number of ways, for example bychecking whether a protocol for encoding is being followed, and thendecoding according to the protocol. This can be performed by thefunctionality that would decode backscattered tag signals under normalcommunication.

In some embodiments, the identification of operation 1522 can beperformed as a result of the decoding of operation 1524, and thereforewith their order interchanged. Indeed, decoding operation 1524 canstart, and if it works for tag signals, it can be inferred that thefourth RF waves detected at operation 1520 were indeed a backscatteredtag signals, hence the identification of operation 1522.

According to an optional operation 1526, an other waveform shapingparameter is interpreted from the tag backscatter decoded at operation1524. The other waveform shaping parameter is distinguishable from theown waveform shaping parameter as per the above, but it can be the sametype of parameter or parameters.

Then according to an operation 1530, the own waveform shaping parameteris adjusted. This takes place similarly to the previously describedoperation 630, but this time in view of the tag backscatter decoded atoperation 1524. If optional operation 1526 has also taken place, thenthe own waveform shaping parameter can be adjusted also in view of theinterpreted other waveform shaping parameter.

Then operations 640 and 650 take place as described previously.

FIG. 15B is a flowchart 1550 illustrating an optional variation of themethod of FIG. 15A. Operations 610 and 1520 are shown again, fromflowchart 1500.

In some embodiments, according to an operation 1515, occurring prior tooperation 1520, third RF waves are transmitted. The third RF waves canthus be transmitted to detect if there are any tags present. Then thefourth RF waves are received from the tags, in response to transmittingthe third RF waves.

The third RF waves can be transmitted from the reader according to theinvention, or not. They can be within the selected channel, or outsideit.

FIG. 15C is a flowchart 1570 illustrating another optional variation ofthe method of FIG. 15A. Operations 1524, 1526, and 1530 are shown again,from flowchart 1500.

In some embodiments, according to a further optional operation 1527, thetag backscatter is error-checked, to discern any possible errors. Thenthe waveform shaping parameter can adjusted also responsive to whetheran error was discerned, and also optionally further as to what the errorwas.

Error-checking can be performed in a number of ways, as can adjustmentresponsive to whether an error was discerned, and even what type it was.A number of such ways are described in copending published U.S. patentapplication Ser. No. 11/388,235 filed on Mar. 26, 2006, entitled “ERRORRECOVERY IN RFID READER SYSTEMS”.

This error-checking feature is particularly useful in embodiments of theinvention that have not caused the fourth RF waves to be transmitted,e.g. by transmitting the third waves of operation 1515. This way, thefourth RF waves that are received in operation 1520 are in response toan action by another reader, instead.

In some embodiments, checking for errors can include comparing theamplitude of a received waveform segment with one or more thresholds. Insome of these, an error is discerned if the amplitude is greater than afirst threshold, or less than a second threshold, or between thethresholds, and so on.

In embodiments where an other waveform shaping parameter is interpretedfrom the decoded tag backscatter, error-checking can be performed onthat other waveform shaping parameter.

In embodiments where the tag backscatter of the fourth RF waves includesa group of symbols, an error can be discerned if a redundant one of thesymbols does not meet a condition with respect to others of the symbols.So, error-checking can be implemented by decoding a parity symbol orsymbols that implement an error-detecting code, such as a cyclicredundancy check (CRC), and/or that implement a correspondingerror-correcting code.

In some embodiments, the own waveform shaping parameter is adjusteddepending on how many errors are occurring. For example, an error countcan be updated in response to discerning an error. Then the own waveformshaping parameter can be adjusted responsive to whether the error countexceeds an error threshold. The error threshold can be set according toa tolerance for errors.

The error-count feature can be used in a number of ways. For example, asecond count can be maintained of how often an error is checked for(“checking events”), and the ratio of the error count to the checkingevents can be compared to a threshold. Additionally, the error count,checking events, or both can be periodically examined and then reset,such as within a time period, or can be maintained and updated withoutresetting (e.g. counting over the lifetime of checking).

FIG. 16 is a flowchart 1600 for illustrating methods according tofurther embodiments. The methods of flowchart 1600 are for adjusting anRFID waveform shaping parameter in view also a performance requirement,and can be performed by the elements described above. The methods offlowchart 1600 include operations 610, 640 and 650 already describedabove, and optionally also operation 620.

According to an operation 1625, a performance requirement is input.Inputting can be performed in any number of ways, such as from a memory,an interface such as a user interface, and so on.

According to an operation 1630, a waveform shaping parameter isadjusted, responsive to the performance requirement. This operation isperformed similarly to how operation 630 is performed, except that theperformance requirement is also heeded. In addition, if optionaloperation 620 has also been implemented and RF energy has been detected,the waveform shaping parameter is adjusted also responsive to thedetected RF energy.

Then operations 640 and 650 take place as described previously.

In some embodiments, the performance requirement is a suitable statisticof performance for an RFID reader system reading RFID tags. For example,the statistic can be a maximum error rate, a minimum tag throughputrate, a minimum signal degradation amount, and so on. Or it can be atime statistic to successfully read one or all of the tags.

In some embodiments, the performance requirement is expressed in termsof a probability. For example, some of the above mentioned or otherstatistics can be expressed in terms of respective probabilities.

In some embodiments, a value for the own waveform shaping parameter isproposed internally. Then a compliance probability is estimated ofwhether the proposed value will cause the performance requirement to bemet. The proposed value is then adopted only if the complianceprobability exceeds a confidence threshold.

In some embodiments, the performance requirement is expressed in termsof a metric, such as in terms of an error rate, a tag throughput rate, asignal degradation amount, a delay, and so on. Then a value for the ownwaveform shaping parameter is computed, which would result inperformance in which that metric is optimized. Then the computed valueis adopted. The same can be also with a combination of such metrics, andso on.

In some embodiments, the performance requirement itself constrains achoice for the waveform shaping parameter. For example, the constrainedchoice can be that of signal encoding. In some particular instances,choices can be constrained for only line codes that permit subcarriermodulation, of the type discussed above with reference to FIG. 12.

FIG. 17A is a flowchart 1700 for illustrating methods according tofurther embodiments. The methods of flowchart 1700 include operations610, 620, 630, 640 and 650 already described above.

According to an operation 1755, a first channel parameter value isstored, which is associated with the waveform shaping parameter that wasadjusted at operation 630, and used in the first channel. This way theadjusted waveform shaping parameter can be later recalled, either inpart or entirely, for reuse in the first channel.

There can be many such types of channel parameter values for a channelsuch as the first channel. For example, the channel parameter value caninclude a designator for the channel, a designator for a parameter ofthe channel, settings for a parameter of the channel, last triedsettings for a parameter of the first channel, and so on.

According to another operation 1760, a second one of the channels isthen selected. Then there is operation in the selected second channel bytransmitting to the RFID tags third RF waves in the second channel andreceiving fourth RF waves backscattered from the RFID tags in responseto the third RF waves. Concurrently with thus operating in the selectedsecond channel, the own waveform shaping parameter is optionallyreadjusted.

According to another operation 1770, the first channel is then selectedagain. This can take place as described in connection with operation610.

According to another operation 1780, the own waveform shaping parameteris reconstructed from the stored first parameter value. This operation1780 is performed in association with operation 1770, meaning they canbe performed in either order or concurrently with each other.

According to another operation 1790, there is RFID operation again inthe reselected first channel, after operation 1760 in the secondchannel. This RFID operation includes transmitting to the RFID tagsfifth RF waves in the reselected first channel, and receiving sixth RFwaves backscattered from the RFID tags in response to the fifth RFwaves. For this operation, at least some of one of the fifth and thesixth RF waves have a waveform with a shape according to thereconstructed own waveform shaping parameter.

FIG. 17B is a flowchart 1756 for illustrating an optional variation ofthe method of FIG. 17A. Operations 1755 and 1780 are shown again, fromflowchart 1500.

According to an operation 1757, first channel usage data is assembledabout operation in the first channel. The first channel usage data isassembled from one or more of the detected RF energy, the first RF wavesand the second RF waves. For example, it can be one or more measurementsabout the detected RF energy and the second RF waves. The first channelusage data can also advantageously include a designator for the firstchannel, a designator for a parameter of the first channel, settings fora parameter of the first channel, last tried settings for a parameter ofthe first channel, performance statistics for a parameter of the firstchannel, and a preference rank for the first channel, etc.

More particularly, within a channel, a reader can choose T→R and R→Tparameters to optimize SNR. A reader may also choose T→R and R→Tparameters to get around interference or to optimize SINR. Thesesettable parameters of operation can be assembled into the first channelusage data.

For a first example, in low-noise channels, a reader may choose tomaximize the link data rate at the expense of signaling robustness,choosing, as one example, a short Tari value. In high-noise channels, areader may choose to maximize link robustness at the expense of datarate, choosing, as one example, a long Tari value.

For a second example, to get around RF interference a reader may choosea Miller subcarrier frequency that places the tag backscatter spectrumaway from the interferer. Also, a reader may set T→R and R→T parametersbased on what it sees other readers are doing. If other readers are indense-reader mode, then it also uses dense-reader mode. Finally a readermay choose its own link parameters based on its own assessment, or onthe combined assessment of it and other readers, both at the currenttime and considering prior times, about the state of the RFIDenvironment.

In these embodiments, in the above mentioned operation 1780, the one ormore own waveform shaping parameters are reconstructed also according tothe first channel usage data. Accordingly, channel operation becomesimproved on an individualized basis.

According to an optional operation 1757, the assembled first channelusage data is stored, such as in a memory. Thus the stored first channelusage data can be recalled, when the waveform shaping parameter is to bereconstructed at operation 1780.

Of course, what is written above about the first channel can be repeatedabout the other channels. So, second channel usage data can be assembledabout operating in the second channel, e.g. from the third RF waves orthe fourth RF waves or both. The second channel usage data can bestored, then later recalled for reconstructing an own waveform shapingparameter for operating in the second channel and so on. This isparticularly useful when an RFID reader system has to hop frequentlyamong different channels.

Furthermore, the parameters of one channel can be compared to those ofthe others. This is especially useful for performance parameters, suchas throughput at each channel, and can be also advantageously impartedin the first channel usage data. And even more, the channel performancestatistics can be compared to each other, to arrive at the abovementioned preference rank for an individual channel relative to theothers. The ranks can in turn be consulted for readers to choosechannels where they expect to result in improved performance statistics,and so on.

According to another optional operation 1772, the first channel usagedata becomes associated with an event. The event can be any convenientevent, such as when operation in the first channel ends. It can also beanother event, such as when interference becomes known or detected tohave started or ended. The associating is preferably in terms of a time,such as by including a time of the event. A time stamp can be included,for example, in the first usage data.

Then, when the waveform shaping parameter is reconstructed, the usagedata can be discounted according to an age of the event. Discounting maybe performed in many ways. For example, if the event is recent, the datais probably still useful. But if an event age is high, such as by nothaving operated in the first channel for a long time, then thecorresponding first channel usage data is not necessarily useful, andcould be ignored. Useful first channel usage data to keep track of thisway include the detected RF energy, such as from the environment. Forthose, if the age is beyond a threshold, the old data can be discardedand new data received and stored.

In addition to merely weighting events based on age (e.g. time sincelast observed), and type (e.g. noise or interference), in someapplications a reader can “learn” the temporal history of theenvironment and take advantage of the predictable recurrence of certainevents. For example, suppose that every 20 minutes an industrialrefrigeration compressor near the reader starts up and momentarilyfloods channels 1 to 5 with RF noise. Knowing this, the reader cansimply avoid these channels at the appropriate times. The reader mayalso choose to occasionally re-survey channels 1 to 5 during the noiseevent, to verify that the temporal or RF nature of the event has notchanged.

In this description, numerous details have been set forth in order toprovide a thorough understanding. In other instances, well-knownfeatures have not been described in detail in order to not obscureunnecessarily the description.

A person skilled in the art will be able to practice the presentinvention in view of this description, which is to be taken as a whole.The specific embodiments as disclosed and illustrated herein are not tobe considered in a limiting sense. Indeed, it should be readily apparentto those skilled in the art that what is described herein may bemodified in numerous ways. Such ways can include equivalents to what isdescribed herein.

The following claims define certain combinations and subcombinations ofelements, features, steps, and/or functions, which are regarded as noveland non-obvious. Additional claims for other combinations andsubcombinations may be presented in this or a related document.

1. An RFID reader system comprising: an antenna; and an operationalprocessing block coupled to the antenna and operable to select a firstone of a plurality of communication channels; identify RF energydetected within the selected channel as a reader system signal fromanother RFID reader system; decode the identified reader system signal;adjust an own waveform shaping parameter responsive to the decodedreader system signal; and cause the antenna to transmit to RFID tagsfirst RF waves in the selected channel such that second RF waves arebackscattered from the RFID tags in response to the first RF waves, inwhich at least some of one of the first RF waves and the second RF waveshave a waveform with a shape according to the adjusted own waveformshaping parameter.
 2. The system of claim 1, in which the RF waveshaving a waveform with a shape according to the adjusted own waveformshaping parameter are the first waves.
 3. The system of claim 1, inwhich the RF waves having a waveform with a shape according to theadjusted own waveform shaping parameter are the second waves.
 4. Thesystem of claim 1, in which the own waveform shaping parameter controlsa choice of a modulation format.
 5. The system of claim 1, in which theown waveform shaping parameter controls a choice of a preamble.
 6. Thesystem of claim 1, in which the own waveform shaping parameter controlsa choice of a signal encoding.
 7. The system of claim 6, in which theown waveform shaping parameter communicates one or a combination: of adata rate, a mode, attributes of a calibration pulse, a rise time, afall time, a pulse shaping, a pulse width, and a preamble.
 8. The systemof claim 1, in which the own waveform shaping parameter represents aprotocol parameter for an RFID system according to a communicationsprotocol.
 9. The system of claim 8, in which the protocol parameterincludes a command for a tag to change its state machine.
 10. The systemof claim 8, in which the protocol parameter includes a command for a tagto respond in a certain manner according to the protocol.
 11. The systemof claim 1, in which the operational processing block is furtheroperable to interpret an other waveform shaping parameter from thedecoded reader system signal, and the own waveform shaping parameter isadjusted responsive to the other waveform shaping parameter.
 12. Thesystem of claim 11, in which the other waveform shaping parametercontrols a choice of a modulation format.
 13. The system of claim 11, inwhich the other waveform shaping parameter controls a choice of a signalencoding.
 14. The system of claim 13, in which the other waveformshaping parameter communicates one or a combination of a data rate, amode, attributes of a calibration pulse, a rise time, a fall time, apulse width, and a preamble.
 15. The system of claim 11, in which theother waveform shaping parameter represents an other protocol parameterfor an RFID system according to a communications protocol.
 16. Thesystem of claim 15, in which the other protocol parameter includes acommand for a tag to change its state machine.
 17. The system of claim15, in which the other protocol parameter includes a command for a tagto respond in a certain manner according to the protocol.
 18. The systemof claim 11, in which the other waveform shaping parameter includes aninterpreted Q parameter suitable for controlling how an RFID taggenerates a random number during an inventorying session, and the ownwaveform shaping parameter encodes a transmitted Q parameter whose valueis determined from a value of the interpreted Q parameter.
 19. Thesystem of 18 in which the value of the transmitted Q parameter is theequal to that of the interpreted Q parameter.
 20. The system of 18 inwhich the other waveform shaping parameter does not include acorresponding ACK command, and the transmitted Q parameter has value ofzero.
 21. An RFID reader system operable to communicate with RFID tags,comprising: selecting means for selecting a first one of a plurality ofcommunication channels; detecting means for detecting RF energy withinthe selected channel; identifying means for identifying the detected RFenergy as a reader system signal from another RFID reader system;decoding means for decoding the identified reader system signal;adjusting means for adjusting an own waveform shaping parameterresponsive to the decoded reader system signal; and antenna means fortransmitting to the RFID tags first RF waves in the selected channel andfor receiving second RF waves backscattered from the RFID tags inresponse to the first RF waves, at least some of one of the first andsecond RF waves having a waveform with a shape according to the adjustedown waveform shaping parameter.
 22. The system of claim 21, in which theRF waves having a waveform with a shape according to the adjusted ownwaveform shaping parameter are the first waves.
 23. The system of claim21, in which the RF waves having a waveform with a shape according tothe adjusted own waveform shaping parameter are the second waves. 24.The system of claim 21, in which the own waveform shaping parametercontrols a choice of a modulation format.
 25. The system of claim 21, inwhich the own waveform shaping parameter controls a choice of apreamble.
 26. The system of claim 21, in which the own waveform shapingparameter controls a choice of a signal encoding.
 27. The system ofclaim 21, further comprising: interpreting means for interpreting fromthe decoded reader system signal an other waveform shaping parameter,and in which the own waveform shaping parameter is adjusted responsiveto the other waveform shaping parameter.
 28. The system of claim 27, inwhich the other waveform shaping parameter represents an other protocolparameter for an RFID system according to a communications protocol. 29.The system of claim 28, in which the other protocol parameter includes acommand for a tag to change its state machine.
 30. The system of claim28, in which the other protocol parameter includes a command for a tagto respond in a certain manner according to the protocol.
 31. The systemof claim 27, in which the other waveform shaping parameter includes aninterpreted Q parameter suitable for controlling how an RFID taggenerates a random number during an inventorying session, and the ownwaveform shaping parameter encodes a transmitted Q parameter whose valueis determined from a value of the interpreted Q parameter.
 32. Anarticle comprising: a storage medium, the storage medium havinginstructions stored thereon, in which when the instructions are executedby at least one component of an RFID reader system that is operable tocommunicate with RFID tags, they result in: selecting a first one of aplurality of communication channels; detecting RF energy within theselected channel; identifying the detected RF energy as a reader systemsignal from another RFID reader system; decoding the identified readersystem signal; adjusting an own waveform shaping parameter responsive tothe decoded reader system signal; and transmitting to the RFID tagsfirst RF waves in the selected channel and receiving second RF wavesbackscattered from the RFID tags in response to the first RF waves, atleast some of one of the first and second RF waves having a waveformwith a shape according to the adjusted own waveform shaping parameter.33. The article of claim 32, in which the RF waves having a waveformwith a shape according to the adjusted own waveform shaping parameterare the first waves.
 34. The article of claim 32, in which the RF waveshaving a waveform with a shape according to the adjusted own waveformshaping parameter are the second waves.
 35. The article of claim 32, inwhich the own waveform shaping parameter controls a choice of amodulation format.
 36. The article of claim 32, in which the ownwaveform shaping parameter controls a choice of a preamble.
 37. Thearticle of claim 32, in which the own waveform shaping parametercontrols a choice of a signal encoding.
 38. The article of claim 37, inwhich the own waveform shaping parameter communicates one or acombination: of a data rate, a mode, attributes of a calibration pulse,a rise time, a fall time, a pulse shaping, a pulse width, and apreamble.
 39. The article of claim 32, in which the own waveform shapingparameter represents a protocol parameter for an RFID system accordingto a communications protocol.
 40. The article of claim 39, in which theprotocol parameter includes a command for a tag to change its statemachine.
 41. The article of claim 39, in which the protocol parameterincludes a command for a tag to respond in a certain manner according tothe protocol.
 42. The article of claim 32, in which when theinstructions are executed, they further result in: interpreting from thedecoded reader system signal an other waveform shaping parameter, and inwhich the own waveform shaping parameter is adjusted responsive to theother waveform shaping parameter.
 43. The article of claim 42, in whichthe other waveform shaping parameter controls a choice of a modulationformat.
 44. The article of claim 42, in which the other waveform shapingparameter controls a choice of a signal encoding.
 45. The article ofclaim 44, in which the other waveform shaping parameter communicates oneor a combination of a data rate, a mode, attributes of a calibrationpulse, a rise time, a fall time, a pulse width, and a preamble.
 46. Thearticle of claim 42, in which the other waveform shaping parameterrepresents an other protocol parameter for an RFID system according to acommunications protocol.
 47. The article of claim 46, in which the otherprotocol parameter includes a command for a tag to change its statemachine.
 48. The article of claim 46, in which the other protocolparameter includes a command for a tag to respond in a certain manneraccording to the protocol.
 49. The article of claim 42, in which theother waveform shaping parameter includes an interpreted Q parametersuitable for controlling how an RFID tag generates a random numberduring an inventorying session, and the own waveform shaping parameterencodes a transmitted Q parameter whose value is determined from a valueof the interpreted Q parameter.
 50. The article of claim 49, in whichthe value of the transmitted Q parameter is the equal to that of theinterpreted Q parameter.
 51. The article of claim 49, in which the otherwaveform shaping parameter does not include a corresponding ACK command,and the transmitted Q parameter has value of zero.
 52. A method for anRFID reader system to communicate with RFID tags, comprising: selectinga first one of a plurality of communication channels; detecting RFenergy within the selected channel; identifying the detected RF energyas a reader system signal from another RFID reader system; decoding theidentified reader system signal; adjusting an own waveform shapingparameter responsive to the decoded reader system signal; andtransmitting to the RFID tags first RF waves in the selected channel andreceiving second RF waves backscattered from the RFID tags in responseto the first RF waves, at least some of one of the first and second RFwaves having a waveform with a shape according to the adjusted ownwaveform shaping parameter.
 53. The method of claim 52, in which the RFwaves having a waveform with a shape according to the adjusted ownwaveform shaping parameter are the first waves.
 54. The method of claim52, in which the RF waves having a waveform with a shape according tothe adjusted own waveform shaping parameter are the second waves. 55.The method of claim 52, in which the own waveform shaping parametercontrols a choice of a modulation format.
 56. The method of claim 52, inwhich the own waveform shaping parameter controls a choice of apreamble.
 57. The method of claim 52, in which the own waveform shapingparameter controls a choice of a signal encoding.
 58. The method ofclaim 57, in which the own waveform shaping parameter communicates oneor a combination: of a data rate, a mode, attributes of a calibrationpulse, a rise time, a fall time, a pulse shaping, a pulse width, and apreamble.
 59. The method of claim 52, in which the own waveform shapingparameter represents a protocol parameter for an RFID system accordingto a communications protocol.
 60. The method of claim 59, in which theprotocol parameter includes a command for a tag to change its statemachine.
 61. The method of claim 59, in which the protocol parameterincludes a command for a tag to respond in a certain manner according tothe protocol.
 62. The method of claim 52, further comprising:interpreting from the decoded reader system signal an other waveformshaping parameter, and in which the own waveform shaping parameter isadjusted responsive to the other waveform shaping parameter.
 63. Themethod of claim 62, in which the other waveform shaping parametercontrols a choice of a modulation format.
 64. The method of claim 62, inwhich the other waveform shaping parameter controls a choice of a signalencoding.
 65. The method of claim 64, in which the other waveformshaping parameter communicates one or a combination of a data rate, amode, attributes of a calibration pulse, a rise time, a fall time, apulse width, and a preamble.
 66. The method of claim 62, in which theother waveform shaping parameter represents an other protocol parameterfor an RFID system according to a communications protocol.
 67. Themethod of claim 66, in which the other protocol parameter includes acommand for a tag to change its state machine.
 68. The method of claim66, in which the other protocol parameter includes a command for a tagto respond in a certain manner according to the protocol.
 69. The methodof claim 62, in which the other waveform shaping parameter includes aninterpreted Q parameter suitable for controlling how an RFID taggenerates a random number during an inventorying session, and the ownwaveform shaping parameter encodes a transmitted Q parameter whose valueis determined from a value of the interpreted Q parameter.
 70. Themethod of 69 in which the value of the transmitted Q parameter is theequal to that of the interpreted Q parameter.
 71. The method of 69 inwhich the other waveform shaping parameter does not include acorresponding ACK command, and the transmitted Q parameter has value ofzero.